The initial phase of a successful pregnancy is composed of a set of transport phenomena. The detached ovum is transported to the ampulla of the fallopian tube, where fertilization may occurs. If fertilization occurred, the embryo enters the uterine cavity within three to four days of ovulation after it has grown to a ball of cells of about 100 μm in diameter. In the uterus, the embryo is conveyed with the uterine fluid for another three to four days to a successful implantation site at the fundus, which is at the upper part of the uterus. The embryo does not have a self propelling mechanism, and thus, it is passively transported with the intra-uterine fluid, which is a highly viscous liquid. Fluid movements within the uterine cavity may be induced by myometrial contractions, which have been observed in non-pregnant uteri via in vivo measurements of intra-uterine pressures and high-speed replaying ultrasound images.